Coral Bleaching ( UPSC Prelims)

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News Context

Australia witnessed unprecedented coral bleaching incidents during the 4th mass coral bleaching event, which began in 2023. This event was characterized by the most severe marine heatwaves along the Coasts.

About Corals

     ○ Composed of invertebrate animals known as polyps that engage in a symbiotic relationship with algae called zooxanthellae, which supply them with nutrients via photosynthesis.
      ○ Typically categorized as either hard coral (reef-building corals) or soft coral.
        ○ Unlike hard corals, soft corals lack calcium carbonate skeletons.
      ○ Types of Coral Reefs: Fringing reef (attached to shores), Barrier reef (separated from the coast by a lagoon), and Atoll reef (ring-shaped with a central lagoon).
      ○ Ideal conditions for coral formation include temperatures of 23-29°C, clear and shallow waters less than 50 meters deep for sunlight penetration, stable salinity, etc.
  ● Coral Bleaching: Occurs when corals are stressed by changes in temperature, light, or nutrients, leading them to expel the symbiotic algae in their tissues, turning completely white and eventually dying due to the loss of their nutrient source.  
      ○ Importance of Coral Reefs: Support approximately 25% of all marine species, including filter feeders (which filter contaminants, e.g., sponges); protect coasts from storms and erosion; have economic value related to tourism, fisheries, etc.
  ● Coral Conservation Technologies: Biorock Technology (uses electrical current to stimulate coral formation with the deposition of calcium carbonate), 3D-Printed Reef Structures, Coral Cryopreservation (for future restoration); the Philippines’ coral larvae cryobank to preserve reef biodiversity by freezing coral ‘seeds’.  

Distribution of Coral reefs

Globally, coral reefs are primarily found in tropical waters. Over one-third of these reefs are situated in Australia, Indonesia, and the Philippines. The Great Barrier Reef in Australia is recognized as the world's largest coral reef system.
 In India, the largest coral reefs are located in the Andaman and Nicobar Group of Islands. Other notable locations include Lakshadweep, the Gulf of Kachchh in Gujarat, the Gulf of Mannar, Palk Bay, and the smaller-scale reefs in Malvan, Maharashtra.
 The Coral Triangle, often referred to as the Amazon of the Seas, is acknowledged as the world’s richest marine biodiversity hotspot.